1. Field of the Invention
The present invention relates to a detecting method and device for touch screens, and more particularly, to a detecting device and method for capacitive touch screens that produces a level image.
2. Description of the Prior Art
A capacitive touch screen determines the locations of touches made by a human body thereon based on changes in detected signals due to its capacitive coupling with the body. When the human touches the screen, noise surrounding the human body also adds to the capacitive coupling between the human body and the capacitive touch screen, and thus causing changes in the detected signals. Moreover, since noise is not constant, it cannot be easily determined. When the signal to noise ratio (S/N ratio) is relatively small, a touch may not be detected, or the location of the touch may not be accurately detected.
In addition, the phase differences between the signals received by the detecting electrodes and the signals which will be provided to the driving electrodes will be resulted because the signals pass through load circuits such as capacitive coupling. When the periods of the driving signals are the same, the signals with different phases will be received at different times. If signals are measured after ignoring the phase differences, the measurements will be disturbed by the different initial phases. If the measurements corresponding to different electrodes are great inconsistent, the determination of the touch position is always incorrect.
Besides, the impedance of the RC circuit, to which the driving signals pass, corresponding to different driving electrodes could be different such that the image values of the touch panel will change roughly when the touch penal is detected in mutual-capacitive coupling.
From the above it is clear that prior art still has shortcomings. In order to solve these problems, efforts have long been made in vain, while ordinary products and methods offering no appropriate structures and methods. Thus, there is a need in the industry for a novel technique that solves these problems.